1. Field of the Invention
The present invention relates to an antilock brake control device for a vehicle having both driven and non-driven wheels, and more particularly to the estimated vehicle speed calculation apparatus of said vehicle.
2. Prior Art
When the brakes are applied to a moving vehicle, the rotational velocity of the wheels decreases, causing the speed of the vehicle itself to also decrease.
However, when the brake force causes such a rapid deceleration of the wheels that the coefficient of friction of the road surface is exceeded, as can happen when the brakes are applied hard and suddenly in an emergency, the wheels tend to lock and the tires slip on the road surface, greatly increasing the danger of the situation. Antilock brake control systems are intended to prevent and release this wheel locking state.
Typically, an antilock brake control device compares the wheel speed with the vehicle speed and begins applying antilock brake control based on various conditions to automatically relax the brake force. One of the conditions used to determine when to start antilock brake control is when the wheel speed is more than a predetermined amount less than the vehicle,speed.
However, while an estimated vehicle speed calculated according to the wheel speed is generally used as the vehicle speed, if the estimated vehicle speed is calculated based on the speed of the wheel to which the brakes are applied or antilock brake control is applied, the difference between the calculated estimated vehicle speed and the actual vehicle speed will be great, and accurate antilock brake control will be difficult to achieve.